Cordierite bodies having honeycomb structures are especially suited for but not limited to use as substrates for catalysts for converting automotive exhaust, for example, or as diesel particulate filters or as regenerator cores. Use of cordierite is favorable in these applications because of its good thermal shock resistance. The thermal shock resistance is inversely proportional to the coefficient of thermal expansion (CTE). That is, honeycombs with low thermal expansion have good thermal shock resistance and can survive the wide temperature fluctuations that are encountered in the application.
In some cases, such as for thin-walled honeycomb substrates, it is desirable to decrease the total porosity so as to increase strength. However, this reduction in porosity results in a decrease in percent loading of the washcoats, which contain the catalysts, so that in some cases it becomes necessary to coat the substrate several times in order to build up a washcoat layer of the desired thickness. This multiple coating process adds cost to the final product. It is desirable for cordierite bodies to have a narrow pore size distribution of pores having a diameter of less than about 10 micrometers. The advantage of a narrow pore size distribution is that it enhances washcoat pick-up so that the desired thickness of the washcoat layer can be achieved with a single coating step without requiring a multiple coating process.
Up to now, a body having both low CTE and narrow pore size distribution in the less than 10 micrometer range has not been achieved. For the above reasons, it would be highly desirable and an advancement in the art to have cordierite bodies with both of these properties. The present invention provides such bodies and a method of making them.